Stimulation of Suicidal Erythrocyte Death by PRIMA-1

Background: The anticarcinogenic drug PRIMA-1 (p53 reactivation and induction of massive apoptosis 1) induces suicidal death of tumor cells, an effect in large part attributed to the up-regulation of the proapoptotic transcription factor p53. Erythrocytes are lacking gene transcription but are nevertheless able to enter eryptosis, a suicidal erythrocyte death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Stimulators of eryptosis include increase of cytosolic Ca2+-activity ([Ca2+]i) and ceramide formation. The present study tested whether PRIMA-1 stimulates eryptosis. Methods: Phosphatidylserine exposure at the cell surface was estimated from annexin V binding, cell volume from forward scatter, [Ca2+]i from Fluo3-fluorescence, ceramide abundance from binding of specific antibodies, and ROS formation from DCFDA fluorescence. Results: A 48 h exposure of human erythrocytes to PRIMA-1 (25 μM) significantly increased the percentage of annexin-V-binding cells without significantly influencing [Ca2+]i or forward scatter. PRIMA-1 (100 μM) induced annexin-V-binding was not significantly blunted by removal of extracellular Ca2+ or by the caspase-3 inhibitor zVAD. PRIMA-1 (100 μM) further increased the ceramide abundance at the cell surface and ROS formation. Conclusion: PRIMA-1 stimulates phosphatidylserine translocation at the erythrocyte cell membrane, an effect at least partially due to up-regulation of ceramide abundance and ROS formation.